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Forces are always defined as either contact or noncontact. Contact forces need to have at least two different objects touching each other to work. They must be able to work together to create physical change. Friction is one of the most common contact forces and can be seen in everything from automobile tires to the way sparks come out of butane lighters. For a force to be considered contact, it must touch something else that makes the force happen.

A noncontact force occurs when the force acts from a distance. An example of a small noncontact force is a refrigerator magnet. This type of magnet is attracted from a distance but will not be able to work from long distances. A larger noncontact force is gravity. Gravity functions from a very long distance but can still have a pull on things that are within the earth due to the strong reactions that it causes. No matter the distance, a force that can cause physical change without physically touching something is a noncontact force.